Comes with the cable and the. This is not an official version of Arduino, but it works with the Official IDE without problem.
In addition to having more input and output ports the Mega model also features more Flash memory, EEPROM and SRAM.
The model must be compatible with all shields and libraries of Uno. Although anything can stop working.
The interface is USB as in UNO.
This Mega version is almost the same price of UNO version, and has more options for use. I think it's worth buying the two, because there's a lot more to support Uno model on the internet. I leave the link to both: